Biphase modulation is important for many electronic products which require digital coding of radio frequency signals, for example, PN coded signals. This type of modulation is often required together with small size, low power draw and robust operation in a broad variety of environments. Examples of such applications include munitions fuzes, radar apparatus and communications systems.
Conventional biphase modulators suffer from lack of flexibility in choosing modulation angles and are typically restricted to 0.degree. and 180.degree. modulation angles. Multiphase modulation schemata (e.g., QAM) typically provide phase angles of integer submultiples of 180.degree. (e.g., 45.degree., 90.degree. etc.). It has been especially uneconomical and impractical to provide close amplitude balance over significant bandwidths between signal portions having different modulation angles, particularly when modulation angles other than submultiples of 180.degree. are required.
Thus, what is needed is a practical, economical apparatus and accompanying method for providing biphase modulation of signals with adjustable phase angles, particularly combined with close amplitude tracking between the two phase states of the modulator, in compact form having low power dissipation and providing robust performance over a broad range of operating conditions.